While they'll "wrap" other shortening services, what's the point now? People won't use them and they'll fall by the wayside. Not really a bad thing in my opinion (people use them now when they don't even need to) but still a bit of a smack in the face to services that essentially helped Twitter in their early days.
"Twitter clients" is a larger term than you realize. I've done banner campaigns, widgets and promotional websites that all display tweets in ways Twitter would be unable to track without this.
While they'll "wrap" other shortening services, what's the point now? People won't use them and they'll fall by the wayside. Not really a bad thing in my opinion (people use them now when they don't even need to) but still a bit of a smack in the face to services that essentially helped Twitter in their early days.